package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;
import java.util.Objects;

/**
 * @author user
 */
public class DefaultSqlSession implements SqlSession, InvocationHandler {

    private final Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);

        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws Exception {
        List<Object> objects = selectList(statementId, params);
        if (objects.size() == 1) {
            return (T) objects.get(0);
        } else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public void insert(String statementId, Object object) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        simpleExecutor.insert(configuration, mappedStatement, object);
    }

    @Override
    public int update(String statementId, Object object) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return simpleExecutor.update(configuration, mappedStatement, object);
    }

    @Override
    public int delete(String statementId, Object object) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return simpleExecutor.delete(configuration, mappedStatement, object);
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, this);
        return (T) proxyInstance;
    }

    private Object query(String statementId, Method method, Object[] args) throws Exception {
        // 准备参数2：params:args
        // 获取被调用方法的返回值类型
        Type genericReturnType = method.getGenericReturnType();
        // 判断是否进行了 泛型类型参数化
        if (genericReturnType instanceof ParameterizedType) {
            return selectList(statementId, args);
        }
        return selectOne(statementId, args);
    }


    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
        // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
        // 方法名：findAll
        String methodName = method.getName();
        String className = method.getDeclaringClass().getName();

        Parameter[] parameters = method.getParameters();

        String statementId = className + "." + methodName;
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Objects.requireNonNull(mappedStatement);
        MappedStatement.ExecutorType executorType = mappedStatement.getExecutorType();
        switch (executorType) {
            case SELECT:
                return this.query(statementId, method, args);
            case INSERT:
                this.insert(statementId, args[0]);
                return null;
            case DELETE:
                return this.delete(statementId, args[0]);
            case UPDATE:
                return this.update(statementId, args[0]);
            default:
                return null;
        }
    }
}
